Continuous process for internally reinforcing salt tablets



Oct. 11, 1960 2,955,982

commuous PROCESS FOR INTERNALLY REINFORCING SALT TABLETS w. c. MOELLERETA;

2 Sheets-Sheet 1 ori inal Filed Jan. 22. 1951 w/zZ/AM c. IMOEZZEA,

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CONTINUOUS PROCESS FOR INTERNALLY REINFORCING SALT TABLETS OriginalFiled Jan. 22. 1951- 2 Sheets-Sheet 2 I NQ K\ I l I r/wmrok UnitedStates Patfinfo A, 2,955,982 lCe Patented Oct. 11, 1950 CONTINUOUSPROCESS FOR INTERNALLY REINFORCING SALT TABLETS Original applicationJan. 22, 1951, Ser. No. 207,078. Divided and this application Oct. 22,1957, Ser. No. 692,021

9 Claims. (Cl. 167-82) This invention relates to a process for preparingingestible tables and more particularly to a method of internallyreinforcing tableted particles of salt so as to render the same moreslowly soluble and thereby preclude discomfort normally caused by quickdissolution of the tablet in the stomach.

As is well known, salt tablets have been used for some time to combatheat exhaustion and excessive sweating, and although the introduction ofsodium chloride into a persons system has proved beneficial in mostinstances, the widespread use of salt tablets has been greatly limitedas many persons develop epigastric discomfort, nausea, or vomitingbecause of the rapid disintegration and absorption of the tablets in thestomach.

* As was disclosed in US. Letters Patent No. 2,478,182,

of August 9, 1949, in the name of William V. Consolazio,

a method has been developed of internally reinforcing compressed tabletsof sodium chloride to render the tablets more slowly soluble in theintestinal tract. The method described therein involves coating orimpregnating the tablets with a material composed of cellulose acetateand/or cellulose nitrate so as to form a waterinsoluble, non-toxic,permeable, membranous film' around amultiplicity of groups of saltparticles contained therein,

2 as set-forth immediately above wherein the tablets are continuouslytumbled as they are advanced along the designated path through thetreatment zone to thereby facilitate impregnation and drying of thesame. I

Also an important object of this invention relates to, the provision ofa method of internally reinforcing salt tablets by submerging the latterin a solution containing a cellulosic derivative and a solvent thereforand wherein the temperature of the solution is maintained lower than thetemperature of the tablets at the moment the, latter are submerged inthe liquid to thereby facilitate impregnation of the tablets.

An equally important object of this invention relates to the provisionof a process for preparing slowly soluble salt tablets as referred toabove wherein a zone of vapor is maintained above the solution so thatas the tablets are removed from the solution and held thereabove todrain excess solution from the same, there is less tendency for. thefilm on the outermost surface to skin and thus 'pre-. clude subsequentremoval of the volatile solvent contained in the tablet.

An additional important object of this invention relates to aneconomical and substantially continuous process for treating salttablets to render the same more slowly soluble wherein the solventremoved from the tablets during the drying thereof is collected andredirected to the solution so that there is little if any solvent waste.

Other important objects of this invention will be obvious from theaccompanying specification and drawings, from which it can be seen that:

Figure 1 is a top plan view of apparatus for substantiallyuninterruptedly treating tablets of granular salt with the" film beingreadily eliminated from system by ex cretion in the feces. Y

The method described by Consolazio involved, compressing the tabletsinto a self-sustaining mass, dipping of the same into a solutioncomposed of acellulosic derivative and a solvent therefor," subsequentremoval, and drying ata temperature sufficient to remove the solventtherefrom. Although this process was found to be opera able, it was notcommercially feasible from an economic standpoint because the cost ofproducing tablets was too high to be practicable in a highly competitivemarket. Manifestly, the tablets must be capable of being manufacturedata minimum cost because they are for the most part, purchased and used bylarge industrial concerns and the armed services who distribute themwithout cost to their employees and members.

It is, therefore, the most important object of this invention to providean economically practicable method of producing slowly soluble,internally reinforced sodium chloride tablets by impregnation withmaterials as disclosed in the said Consolazio patent.

A further important object of this invention relates to the provision ofa process for internally reinforcing salt tablets with a cellulosicderivative wherein'thetablets are continuously advanced along apredetermined path of a cellulosic material to internally reinforce thesame;

Fig. 2 is a longitudinal, vertical, sectional view taken on line Il-IIof Fig. 1;

Fig. 3 is an enlarged, transverse, cross-sectional view taken on lineIII--III of Fig. 2; and I Fig. 4 is a fragmentary, sectional viewsimilar to Fig. 2 illustrating a modified embodiment of the invention.

Although the method herein disclosed is essentially adapted for theimpregnation of sodium chloride tablets to internally reinforce thesame, manifestly the process could be utilized for other similar tabletswith ,various modifications and compensatory adjustments as maybenecessary.

- Briefly, thev instant process contemplates continuously V advancingand tumbling the tablets to be impregnated along a predetermined paththrough a plurality of successive treatment zones. By virtue of theprovision of the equipment to be hereinafter described, the tablets tobe treated may be introduced into the apparatus at one end thereof,impregnated with a special material, excess travel through a pluralityof zones whereby an unintercontinuous process for internally reinforcingsalt tablets solution drained from the tablets after impregnation withthe material, and the tablets subsequently dried. so that a finishedproduct ready for packaging emanates from the opposite end of theapparatus. The first step in the method of the present invention forforming internally reinforced sodium chloride tablets con: sists ofproducing salt tablets from particles of sodium chloride by diecompression in a conventional tableting machine 12. Manifestly, theamount of salt contained in each tablet 10 will vary with the pressureof machine 12 and, inasmuch as it is desirable to have a highly porous,cellular tablet 10 which may be readily impregnated, itis extremelyimportant that the pressure placed on tablets 10 in compression machine12 be closely controlled. In order to render the tablets self-sustainingwhile still re; maining in a highly porous condition it is preferablethat the tablets be formed at a pressure within therange offj to 8 tonsper square inch. Tablets compressed within range may be easilyimpregnated with a suitable com tion and are slowly soluble in'thedigestive tract.

\ l ,3 The size of the sodium chloride particles for producing tabletsmay vary and the tablets may be of any convenient dimensions butproduction of a standard 10 grain tablet meets many of the consumersspecifications.

, Inthe embodiment of the present invention illustrated in Figs. 1 to 3inclusive of the drawings, tablets 10 produced by compression tabletingmachine 12 are allowed to gravitate along an inclined tubular conduit 14into a hollow tank broadly numbered 16. It can be appreciated that thetime interval lapsing between the time the tablets 10 are produced inmachine 12 and ultimately enter tank l6'is relatively short.

Tank 16 is most usually of rectangular configuration having an open topwith a removable closure situated thereon, and is adapted to receive aliquid impregnating substance 18 which is maintained at a predeterminedlevel within the tank 16 from a suitable supply distribution system notherein shown.

As disclosed in the Consolazio patent, various materials may be used forinternally reinforcing the salt tablets, but the most effectiveimpregnating or coating agents have been found to be cellulosederivatives, particularly cellulose acetate and cellulose nitrate. Also,as pointed out in the reference patent, best results were obtained froma low viscosity, high acetyl, cellulose acetate. For impregnatingpurposes, the cellulosic material is dissolved in a suitable solventwhich may be readily removed by evaporation, most usually accmplished byheating and, although many types of solvents would be feasible, from acommercial standpoint acetone has been found to be the preferredmaterial. A solution containing 30% ,cellulose acetate in acetone is themost desirable impregnating liquid. The salt tablets 10, directed intothe cellulosic material 18 are channeled by conduit 14 into anelongated, open top trough 20 disposed within tank 16 at a diagonalangle, as is illustrated in Fig. 2. It can be seen that trough 20 issubstantially longer than the diagonal, longitudinal length of tank 16and therefore, the uppermost end of trough 20 extends through an openingprovided therefor in one end wall 24 of tank 16. The lowermost end oftrough 20 is disposed below the surface of liquid 18 so that as tabletsare directed into trough 20 from conduit 14, they are submerged inliquid 18.

7 Since conduit 14 extends through end wall 22 of tank 16 and isdisposed to direct tablets 10 into the lowermost end of trough 20disposed adjacent the bottom of tank 16, it can be recognized that astablets 10 are advanced upwardly in trough 20 by screw or helix conveyor26, tablets i 58 fall through the perforations of plate 52 into a largercontainer 59 within which receptacle 56 is disposed. Therefore, thetablets in receptacle 56 are ready for immediate packaging and shipmentand no additional operations are necessary.

By virtue of the provision of the conveyors 26 and 40, it can now beappreciated that a substantially continuous process of impregnatingtablets 10 is provided inasmuch as tablets 10 emanating from machine 12describe a continuous path of travel until being deposited in receptacle56. In other words, tablets 10 pass along a predetermined path of travelthrough the apparatus and are successively treated in a plurailty ofzones. In the first zone, the tablets 10 are submerged in liquid 18 soas to completely impregnate the same, and it is pointed out that it isdesirable to maintain the temperature of liquid 18 at least as low asthe temperature of tablets 10 at the moment the latter pass intosolution 18. It is preferable, however, that the temperature of liquid18 be maintained substantially below the temperature of tablets 10 asthey gravitate into liquid 18 and, since the temperature of tablets 10at the moment the latter enter solution 18 is substantially about 110F., solution 18 should be maintained at approximately 90 F. Maintenanceof the tem- 10 remain in liquid 18 for a relatively long period of timei to effect complete impregnation of the same. Helix 26 is rotatablymounted in trough 20 and is actuated by a suit- 'able prime moversuch asan electric motor 28 coupled to a speed reducer 30, and an endless chain32 which is in turn connected with the uppermost end of helix 26exteriorly of tank 16 so that screw 26 is rotated at a predeterminedspeed to move tablets 10 up trough 20.

From the uppermost end of trough 20, impregnated tablets 34 arepermitted to gravitate along an inclined outlet spout 36 at theuppermost end of trough 20 located i exteriorly of tank 16, into anelongated, hollow drying compartment broadly numerated 38 that is alsoprovided with a substantially horizontal, elongated helix or screwconveyor 40. Compartment 38 is also provided with a suitable heater 42which extends longitudinally of helix 66. Because of the provision ofplate 52, separation and sorting is accomplished inasmuch as undersizedtablets perature differential between tablets 10 and liquid 18 is ofimportance because of the fact that as the relatively hot tablets 10enter solution 18, which is kept at a lower temperature, cooling oftablets 10 causes the solution 18 to be pulled into the interstices ofthe cellular tablets 10 at a faster rate than would otherwise beeffected. In other words, if tablets 10 were at a lower temperature thansolution 18, because of the characteristics of the solvent in liquid 18and the nature of the cellulosic derivative, the impregnation of tablets10 would be somewhat retarded.

In order to maintain the proper temperature differential between tablets10 and impregnating solution 18, tablets-10 may be heated by externalmeans (not shown), although in actual practice it has been found thatcompression of the particles of sodium chloride in the stamping ortableting machine 12 heats the tablets 10 to a sufficient temperaturethat they are within the prescribed range at the time they entersolution 18. It can be appreciated that because of the relatively shortpath of con duit 14, as well as the substantially enclosed naturethereof, there is little loss of heat as tablets 10 gravitate frommachine 12 into liquid 18. The helix 26 advances tablets 10 up trough 20into a second treatment zone located above the free surface of liquid 18and in this zone, excess liquid 18 is drained from impregnated tablets34 and which flows back into 1iquid 18. Manifestly, since tank 16 is aclosed container, there is a zone of acetone vapor above the surface ofliquid 18 within which the tablets 34 are disposed, and because of themaintenance of this vapor zone within which tablets 34 are located,there is less tendency for the cellulosic material present on theoutermost surface of tablets 34 to skin or form a relatively hardoutermost layer. The importance of this anti-skinning process will behereinafter pointed out but it can be perceived that the cellulosicmaterial remains in a relatively soft condition on the outermost surfaceof tablets 34.

' ,As tablets 34 reach the uppermost end of trough 20, they are directedinto a third treating zone via spout 36 wherein.allvolatilesolventmaterial is removed from tablets 34. In the third treatment zone, thetablets are advanced continuously along the length of compartment 38 sothat when the tablets reach spout 50, all solvent has been removedtherefrom.

The apparatus herein described is adapted to impregnate and subsequentlydry tablets 10 as they are continu ously advanced along a predeterminedpath of travel and in this respect, it can be seen that the impregnationand drying can be varied at will by merely changing the revolutions perminute of helix 26 and helix40 and by varying thetemperature'withincompartment 38. Utilizing spasms a IO-gr'ain tablet 10 and a 30%solution of cellulose acetate in acetone,'it is desirable to rotatehelix 26 at a speed such that tablets 10 are submerged, in liquid 18 forapproximately 3 to 5 minutes and maintained in the zone above liquid 18for a time so that the outermost coating on tablets 34 is keptrelatively soft, but not such that tablets 34 become sticky and tend toagglomerate.

The speed ofmanufacture of tablets 34 may be tremendously' increasedthrough'the use of heater 42 m compartment 38,'and it has been foundtbat by maintaining the temperature within compartment 38 atapproximately 120 F. to 140 R, the solvent will be drawn oif completelyat a rapid rate and the tablets 34 emanating from spout 50 are incondition for packaging. The speed of rotation of helix 40 shouldpreferably be regulated to maintain the tablets 34 within the chamber 38for a period within the range of from 5 to 15 minutes so that. allsolvent is removed from tablets 34 in this third zone.

A more economical process may be produced by evacuation of compartment38 so that the solvent vapor removed from tablets 34 may be redirectedinto solution 18 located within tank 16 and therefore, in this respect amanifold 60, coupled with compartment 38 is joined with a suitablesuction blower 62 that is in turn driven by a prime mover 64. A line 66also interconnects blower 62 and the container 59 for removing vaporfumes adjacent the outlet end of compartment 38, inasmuch as there issome tendency for the vapor to emanate from spout 50 and be collected incontainer 59. It can be ascertained that the outlet conduit of suctionblower 62 may be connected to the means for directing cellulosicmaterial into tank 16 and it is also of advantage to provide a suctionpump 68 in communication with tank 16 near the bottom thereof, so thatliquid 18 may be recirculated into tank 16 by means of pipe 72. Motor 70is provided for driving suction pump 68 at a predetermined rate ofspeed.

Tablets 10, compressed into a self-sustaining body by machine 12 areinternally reinforced by the cellulosic material by virtue of thematerial forming a water insoluble, nontoxic, permeable, membranous film.around a multiplicity of groups of salt particles contained therein andtherefore, the tablets are rendered slowly soluble in the intestinaltract as hereinbefore pointed out. The method of impregnating sal-ttablets as accomplished by the continuous process disclosed ismaterially improved by virtue of the fact that the tablets arecontinuously tumbled as they are moved through the plurality oftreatment zones and therefore, all sides of the tablets are subjected tothe various treatments with no tendency of agglomeration or the like.

It is imperative that the salt tablets emanating from machine 12 beabsolutely free of moisture and ordinarily, the heat derived by pressurein the machine 12 will remove the moisture content. However, in theevent it is desired to further treat the tablets 10 so far as moisturecontent thereof is concerned, there may be provided conveyor tube 100(Fig. 4) for receiving the tablets from the machine 12 by conduit 102corresponding to conduit 14. The tube 100 in turn communicates with tank104 corresponding to tank 16 by means of an inclined pipe 106. The salttablets 10 are moved through the tube 100 by means of a horizontal helixconveyor 108 driven by motor 110 to discharge the tablets into the pipe106 and thence into a foraminous receiving hopper 112 within tank 104. Aplurality of strip-heating elements 114 within tube 100 supply thenecessary heat to cause removal of the moisture from the salt tabletsand a suction blower 116 communicating with the tube 100 draws off thehumidity.

It is seen that the above method is adapted for impregnation of salttablets by a substantially uninterrupted process which may be easilyaccomplished by one person overseeing the entire operation, and thetablets may be rendered substantially non-nauseating at a very lowincrease in unit price. The apparatus itself is of low. cost, relativelyinexpensive in maintenance and operation and is substantially free ofintricate parts which are liable.

to break down. Although the preferred process has been set forth indetail herein, it is manifest that various modificationsin the steps ofprocedure as well as the operating conditions can be made withoutdeparting from the concepts of this invention and therefore, it isintended to belimited only by the scope of the appended claims. This isa, division of application Serial No. 207,078, filed January 22, 1951and now abandoned.

Having thus described the invention what is claimed as new and desiredto be secured by Letters Patent is:

1. In a method of preparing an internally reinforced, slowly solublesalt tablet wherein a multiplicity of groups of salt particles are eachsurrounded by a membrane composed of a cellulosic derivative, the stepsof compressing particles of salt into a self-sustaining, highly poroustablet; submerging the tablet in a liquid composition consistingessentially of a film forming cellulose derivative and a solventtherefor; maintaining the temperature of the liquid composition lowerthan the temperature of the tablet at the moment the latter is submergedin the liquid composition; removing the tablet from the liquidcomposition; allowing the excess of liquid to drain from the table; andthereafter drying the tablet.

2. A method as set forth in claim 1 wherein the differ ence between thetemperatures of the tablet and liquid composition is about 20 F.

3. A method as set forth in claim 1 wherein the temperature of saidtablet is about 110 F. and the temperature of said liquid composition isabout F.

4. In a method of preparing an internally reinforced, slowly solublesalt tablet wherein a multiplicity of groups of salt particles are eachsurrounded by a membrane composed of a cellulosic derivative, the stepsof maintaining a bath of a liquid composition consisting'essentially ofa film forming cellulose derivative and a solvent therefor; maintaininga zone adjacent said bath of said solvent in vapor form; submerging thetablet in the bath; removing said tablet from the bath; and supportingthe tablet in said vapor zone until excess liquid has drained therefromwhereby said zone of vapor retards skinning of the film on the surfaceof the tablet during the draining operation.

5. In a method of preparing an internally reinforced, slowly solublesalt tablet wherein a multiplicity of groups of salt particles are eachsurrounded by a membrane composed of a cellulosic derivative, the stepsof compressing particles of salt into a self-sustaining, highly poroustablet; submerging the tablet in a liquid composition consistingessentially of a film forming cellulose derivative and a solventtherefor, the temperature of the liquid composition being maintainedlower than the temperature of the tablet at the moment the later issubmerged in the liquid composition; maintaining a, vapor zone adjacentsaid liquid compositiom'removing the tablets from the liquidcomposition; supporting the tablet in said vapor zone until excessliquid has drained therefrom whereby said zone of vapor retards skinningof the film on the surface of the tablet during the draining operation;and thereafter drying the tablet.

6. In a process for preparing slowly soluble salt tablets whereinparticles of salt are initially compressed into selfsustaining, highlyporous tablets, the improved method of internally reinforcing thetablets by placing a mem brane composed of a cellulosic derivativearound a multiplicity of groups of salt particles contained thereinwhich include the steps of substantially continuously advancing aplurality of the tablets along a predetermined path of travel through aplurality of zones; submerging the tablets in a liquid composition.consisting essentially of a film forming cellulosic derivative and asolvent therefor in a first zone; removing the tablets from the same andsupporting the tablets in another zone to drain excess liquid therefrom;and heating the tablets to a preaeaeesa 7 determined temperaturein athird zone todry thetablets by removing all of the solvent therefrom. I

7. A method as set forth in claim 6 whereinthe tablets are substantiallycontinuously tumbled as they are continuously advanced through saidplurality of zones. 8. A method. as set forth in claim 6 wherein saidsolvent removed from the tablets in said third zone is collected andthen directed to the liquid composition in the first zone.

9. 'In a process for preparing slowly soluble salt tablets whereinparticles of salt are initially compressed into selfsustaining, highlyporous tablets, the improved method of internally reinforcing thetablets by placing a membrane composed of a cellulosie material around amultiplicity of groups of salt particles contained therein which includethe steps of substantially continuously advancing a plurality of thetablets along a predetermined path of travel through a plurality ofzones; submerging the tablets at a first zone and while at a temperatureof approximately 110 F. in a liquid composition at a temperature ofapproximately 90 F. and consisting essentially of a film-formingcellulosic material dissolved in a relatively volatile organic solventtherefor; removing the tablets from the composition and supporting thetablets in an References Cited in the file of patent UNITED STATESPATENTS 1,690,760 Volwiler Nov. 6, 1928 2,410,110 Taylor Oct. 29, 19462,478,182 Consolazio Aug. 9, 1949 2,512,192 Yen June 20, 1950 OTHERREFERENCES Rowell: The Art of Coating Tablets, Drug and Cos. Ind.,September 1948, vol. 63, No. 3, pp. 308, 309, 310,

20 411, 412, 413 and 414.

1. IN A METHOD OF PREPARING AN INTERNALLY REINFORCED, SLOWLY SOLUBLE SALT TABLET WHEREIN A MULTIPLICITY OF GROUPS OF SALT PARTICLES ARE EACH SURROUNDED BY A MEMBRANE COMPOSED OF A CELLULOSIC DERIVATIVE, THE STEPS OF COMPRESSING PARTICLES OF SALT INTO A SELF-SUBSTAINING, HIGHLY POROUS TABLET, SUBMERGING THE TABLET IN A LUQIUD COMPOSITION CONSISTING ESSENTIALLY OF A FILM FORMING CELLULOSE DERIVATIVE AND A SOLVENT THEREFOR, MAINTAINING THE TEMPERATURE OF THE LIQUID COMPOSITION LOWER THAN THE TEMPERATURE OF THE TABLET AT THE MOMENT THE LATTER IS SUBMERGED IN THE LIQUID COMPOSITION, REMOVING THE TABLET FROM THE LIQUID COMPOSITION, ALLOWING THE EXCESS OF LIQUID TO DRAIN FROM THE TABLE, AND THEREAFTER DRYING THE TABLET. 